God is not an Entity?

What you said was that God was "immanent". That means that God is in everything, including rocks. All you are saying in reply seems to be that God has a property of immanence, not that God is immanence. So you don't want to claim that any specific thing is God, just that your deity has the property of being in all things that exist. Nobody here denies the existence of physical reality, but atheism is still about denying the existence of your god (along with others) as entities that merit worship. You do worship your god, don't you? That is, you attend church services and pray to it. You have some idea of its nature that goes beyond the mere property of immanence. It is the nature of this entity that we are discussing, not just one aspect of it.

As I've been at pains to explain elsewhere, definitions are not to be confused with meaning. They are merely succinct descriptions of word senses. They are heuristic in that they allow people to discover the full meaning of a particular sense by distinguishing the usage of that sense from other senses of the word and from words with similar meanings. So a more appropriate description of what any of us mean by "god" or "deity" would be a list of properties that are more or less true of it. Not all uses of the word will have all of the same properties or all of those properties to the same degree.

What might such a list look like? Perhaps something like this:

A god is an entity that is...

1. Immaterial (i.e. a spirit)
2. Intelligent
3. Emotional (i.e. has likes, dislikes, desires, moods...)
4. Able to manipulate reality at will (i.e. perform miracles)
5. Very powerful
6. Immortal
7. Extremely knowledgeable
8. Worshiped by people
9. Benevolent (i.e. worthy of worship)
10. Influenced by worship and prayers
11. Etc.

The list of properties need not be comprehensive for our purposes, and there will be some instances of word usage that do not include all properties on the list. This is the kind of entity that atheists reject belief in.

Your god represents a subclass of this kind of entity. We could describe it with a list of additional properties:

God is...

1. A god
2. Immanent
3. Omnipotent
4. Omniscient
5. Omnibenevolent
6. The creator of physical (material) reality
7. Singular (i.e. there are no other gods)
8. The specific god referenced in the Christian Bible
9. Etc.